1. Field of the Invention
The present invention relates to a method for lining pipe lines used for transporting city water, city gas, petroleum and other various kinds of fluids for the purpose of repair or reinforcement of these pipe lines, and more particularly, to a method for lining pipe lines, especially underwater pipe lines, such as those laid on the bottom of a sea; lake or river, wherein a flexible lining material is applied onto the inner surface of such pipe lines.
2. Discussion of Prior Art
From the past, a variety of methods have been proposed as a means for lining pipe lines. In U.S. Pat. No. 3,381,718, for example, there is disclosed a method for lining concrete pipe lines, especially those for sewers through which a corrosive liquid is passed, wherein an acid- and alkali-resistant plastic sheet is applied onto the inner surface of the concrete pipe lines. This plastic sheet is a laminate comprised of a fabric of a fibrous material, such as cotton, synthetic fibers or glass wool, overlaid with a vinyl chloride resin according to a calendering, coating or the like means, and is shaped in a tubular form by the aid of a special cylinder. In this U.S. patent wherein the plastic sheet is inserted into a concrete pipe line and then inflated for lining the pipe line, the method is troublesome in its operation per se and is not suited for lining long pipe lines. A binder used in this U.S. patent for bonding a tubular lining sheet to the pipe lines is an epoxy resin generally utilized in a dry state (See Col. 3, lines 7-13).
In U.S. Pat. No. 4,009,063, there is disclosed a method for lining a pipe line having manholes with a hard rigid pipe of thermosetting resin. The pipe for lining used in this patent is manufactured by immersing a tubular fibrous felt in a resin to form a pipe comprising an impervious film on the inner side thereof and a curable resinous layer on the outer side thereof. An inflatable tube is inserted into the pipe and the tube is inflated in a pipe line to attain its lining with the pipe being laid on the tube. This method is not suited as a method for lining pipe lines buried in the ground and cannot be used for lining long pipe lines, particularly those having bends. In this U.S. patent, a polyester resin and an ordinary epoxy resin are used as general curing resins (See Col. 10, lines 11-23).
There is also known a method for lining pipe lines which is carried out in such manner that a flexible lining material in the form of a tube previously provided on the inner surface thereof with a binder is inserted into a pipe line and allowed to advance therein while turning the lining material inside out under fluid pressure whereby the lining material is bonded onto the inner surface of the pipe line by the aid of the binder. According to this method, it is unnecessary to dig up a pipe line over its full length and the method is operable simply at both terminal ends of the pipe line. The lining work itself can be done even for a long pipe line and within a short period of time, thus being regarded as an excellent method in recent years (See U.S. Pat. Nos. 4,064,211, 4,368,091 and 4,334,943).
In the above mentioned U.S. Pat. No. 4,064,211, there is disclosed the so-called evagination-lining method wherein one end of a tubular lining material provided on the inner surface thereof with a binder is fastened and bonded in an evaginated state to one end of a pipe and a liquid is inserted from the other end of the pipe into the interior of the pipe whereby the tubular lining material is allowed to advance within the pipe line under fluid pressure while being turned inside out to attain the lining of the pipe line. After completion of the evagination-lining operation, a small tube is inserted into the lined pipe line and a warmed liquid is circulated to accelerate curing of the binder. In this method, the circulation operation of a warmed liquid after application of the lining material onto the inner surface of the pipe line is troublesome; a considerably large amount of the warmed liquid is required in case of lining a long pipe line, and so the operation for circulation and warmth-keeping of such a large amount of the warmed liquid is very troublesome. In particular, it is difficult to bond the lining material completely onto the inner surface of the pipe line when the pipe line is inclined or bent in a vertical direction. An epoxy resin is disclosed in this U.S. patent as the binder used therein (See Col. 3, lines 5-6).
The evagination-lining methods disclosed in the above-mentioned U.S. Pat. Nos. 4,368,091 and 4,334,943 enable control of the fluid pressure required for evagination of the lining material by the aid of a pressure container, and concurrently adjustment of the amount of a binder to be supplied onto the inner surface of the lining material. The method disclosed in the latter mentioned patent is especially excellent in that the lining operation can be carried out, without forming any wrinkles in the lining material and forming a narrow path in bend portions of the pipe line, by adjusting the speed of the lining material in its advancing movement within the pipe line by the aid of a special evagination-inducing belt drawn from the opposite side of the pipe line. Since the binder used in this method is an epoxy resin, however, there is a problem in using this method for lining of a pipe line having a length as long as several thousand meters in view of a limited pot life of the binder to be used.
In principle, the evagination-lining method just mentioned above is applicable to a pipe line irrespective of its length. Actually, however, the method is applicable to a pipe line having a length as long as several hundred meters but is hardly applicable directly to one having a length beyond that length.
In case the lining treatment is carried out according to this method, the pipe line is treated with a scraper or the like to remove rust, etc. thereon, washed with water and then dried prior to introduction of a tubular lining material under evagination.
As mentioned above, the pipe line and the lining material are bonded by the aid of a binder. As both the lining material and the pipe line are of air-impervious materials, however, a binder containing a volatile substance such as a binder of rubber type cannot be used. Among binders now conventionally employed, therefore, any binder other than those of the reaction-curing type can be used. The reactioncuring type binder is advantageous in that when it is cured in the state of being impregnated, in a large amount, into the lining material, the binder will form a rigid pipe inside the pipe line after curing, which pipe will maintain the function of a flow path to prevent leakage of a fluid even if bonding of the lining material is partially insufficient or the pipe line itself is broken by external force.
In the above mentioned evagination lining method wherein a binder is prepared and then applied onto the inner surface of a lining material and thereafter the lining material is introduced into the pipe line under evagination, it takes a longer time for such a series of steps and the binder must not be cured during the steps.
As the pipe line becomes longer, it proportionally takes a longer time for the application of the binder and for the introduction of the lining material into the pipe line. Consequently, the binder should proportionally have a sufficiently longer pot life. However, a binder having a longer pot life requires a longer time for its curing. Thus, a longer time is needed for a period from the insertion of the lining material to the completion of curing of the binder, and as a result, the time needed for the whole treatment becomes longer.
Under such circumstances, European Laid-open Pat. application No. 155,406 discloses the use of a precurable acrylic binder based on photopolymerization for curing the applied binder without using any warming medium. According to this method, the evagination-lining treatment is carried out using, as a binder, a curable resin containing a catalyst which can initiate polymerization by radiation by actinic light, and at the same time, irradiated light is introduced into the lining material to cause early curing. In this method, however, it is troublesome to introduce an irradiation light source to the lining material applied to a long pipe line. Further, a light having a specific wave length capable of exciting the catalyst is necessary in this method, thus making it practically unattractive.
In the conventional evagination-lining methods, the length of the pipe line in the working section is usually limited to about 2-300 meters for the various reasons above mentioned. It is the current status, therefore, that the lining treatment for a long pipe line system be accomplished by repeating the pipe-lining work for short section of the pipe line.
The present invention has been accomplished in view of the above situation, and its object resides in an improvement relating to conventional evagination-lining methods and in providing a method which can line a long pipe line having a length of several thousand meters or more in a simple operation.